Method of manufacturing paper and/or board



June 16, 1942. A. TUTEN METHOD OF MANUFACTURING PAPER AND/0R BOARD FiledJuly 11, 1939 m NZ WW m7 W A been known in Europe for many years.

Patented June I 16, 1942 UNITED METHOD MANUFACTURING I APER AND/OR BOARDAlvin Tuten, Georgetown, S. 0., assignor, by mesne assignments, toInternational Paper Company, New York, N. Y., a corporation of New YorkApplication July 11, 1939, Serial No. 283,755

1 Claim.

' that it will take readily and evenly glue or other adhesive used inmaking the corrugated board and that the other surface will possesscharacter-. istics as to permit a smooth and even application ofprinting inks.

Board of the type above described has been i made on the so-calledmulticylinder board machine where individual webs ofmatrial possessingthe desired characteristics are first formed For example, in themanufacture and thereafter united in the usual manner well known tothose skilled in the art. However, due

to the inherent characteristics of this form of paper or board machine,it can be run only at comparatively slow speeds and the resultantproduct, although possessing the desired surface characteristics, has adecided tendency to split along the lines where the individual webs havebeen joined during the paper or board making process. In fact by a merevisual examination of a cylinder board it is possible to determine thelinesof demarcation between the individual webs.

Use of amultiple headbox system in conjunction with a Fourdrinier papermachine is not new. In fact the so-called Diana machine has Reference isalso made to United States Patents Nos. 2,018,382; 2,098,733; andReissue Letters Patent 20,667 taken out in the nameof John W. Sale.Undoubtedly other patents disclosing a multiple headbox system for themanufacture of paper or board on a Fourdrinier machine are known to theart. The above mentioned inventor, John W.

Sale, has explored in a preliminary waythe problem of manufacturingmulti-ply paper or board method of operating a multiple headbox systemfor the manufacture of paper or board. Briefly, g, that inventionrelates specifically to a process wherein stock flowing from the primaryheadbox is formed into a sheet and dehydrated sufliciently to permitoperation of a dandy roll in advance of the secondary headbox. The dandyroll not only functions in a conventional manner, but servesparticularly to iron out both inequalities of caliper and uneven spotsin the primary sheet and thus to present to the stock flowing from thesecondary headbox a substantially uniform surface with the eliminationof high spots. This effectually prevents localized showing through ofparts of the base sheet which, possessing characteristics differing inmany cases from the characteristics of the secondary stock, wouldotherwise be definitely detrimental to the printing qualities of thefinal board.

An object of my present invention which constitutes an improvement overmy earlier application is to define definite optimum basic operatingconditions for the regulation of the action of the primary headboxrelative to that of the secondary headbox.

A further object of this invention is to provide a method and means forthe accurate control of the action of the primary headbox relative tothat of the secondary headbox based on easily observable data.

A still further and more specific object of this invention is to defineoptimum operating conditions for the primary and secondary headboxrelative to the speed of the fourdrinier wire and to provide a method ofcontrolling these operations based on easily observable data.

These and other objects will be made clear as the detailed descriptionceeds.

In the'drawing I have represented schematically a paper or board machineof the fourdrinier type showing a fourdrinier wire having mountedthereover a secondary headbox embodying the principles of my inventiontogether with the conventional form of primary headbox.

Papermaking has been, and probably for many years will be, one of themost empirical of all major industries due to the fact that themanufacturing process from the woodpile to the freight car involves notonly a tremendous number of variables, but many variables which arebeyond control. In the manufacture of board, particularly, themanufacturing units are very large, operate at great speeds, and thesystem at any given moment frequently contains as much as e of theinvention protons of board making material between the beaters or mixingtanks and the reel receiving the finished paper. Accordingly, when achange in the character of the material being supplied to the papermachine becomes apparent due to a falling ofi of some desiredcharacteristic of the finished goods, operating changes must be made tocorrect the condition and the changes may have to be dispensed with veryshortly after they are put into effect. As used hereafter the termoptimum condition has reference to a condition of operation whichproduces the best results most of the time. Temporary contingencies mayarise which will necessitate temporary adjustments of one or morefactors to points radically difierent from optimum conditions, but suchdepartures are strictly temporary and the optimum condition will bereverted to as soon as the effect of whatever disturbing factor may havearisen has subsided.

The pointwhich must constantly be kept in mind in discussing theoperating of a Fourdrinier machine is that the Fourdrinier machine isessentially a continuous process machine whereas the manufacture of pulpis essentially a batch process. Variations in pulp may occur between theseveral batches which will be delivered seriatim to the Fourdrim'ermachine and these variations must be compensated for, first,

by the treatment of the pulp between the diffusersand the Fourdriniermachine, e. g., beating and/or jordaning, etc., and second, byadjustment of the operating characteristics of the Fourdrinier machineitself.

Whatever characteristics the finished product is to. have aresubstantially fixed by the time the sheet leaves the press rolls andgoes to the dryer. The present press and drying rolls are capable ofrelatively few adjustments which have any appreciable effect on thequality of the sheet and therefore the major adjustments in ,theFourdrinier machine to meet varying conditions must be made at the wetend.

Fundamentally the headbox of a paper machine is operated at a pressuresuificient to give the stock emerging from the headbox a velocityapproximating the lineal speed of the Fourdrinier wire. This velocity isstrictly a function of the static pressure on the stock adjacent theslice opening whether the box be of the gravity velocity of emergence ofthe stock should be proportional to the square root of the static headexpressed in feet .of water. Naturally, the efiect of baflies and floweveners in the headbox is to reduce the actual velocity of emergence ofthe stock below the velocity theoretically obtainable byvirtue of anyparticular head. The quantity of stock emerging is a function of boththe velocity and the degree of opening of the slice.

The paper or board machine, particularly as' used in the Fourdrinierboard industry, is apt to be of a width approximating 200" and theextent of the slice opening usually varies across the width of themachine to take care of local variations caused by eddy currents. As aresult, adjustment of the slice opening is a rather delicate operationand not one to be resorted to for any quick change. If, for example, dueto a change in the character of the'pulp coming to the machine theheadbox consistency were to increase eriously the number of cubic feetper minute of stock emerging 'from the headbox would have to be reducedin order to maintain constant the basis weight of the sheet beingquently the quantity of stock emerging.

What has thus far been described is standard papermaking practice andapplies equally" to multiple headbox operation and to single headboxoperation. I have discovered, however, that for the multiple headboxoperation certain operating characteristics, if maintained as closely aspossible within the limits hereinafter set forth, will yield the bestresults in producing a uniformly desirable finished product. Thesecharacteristics are as follows:

1. The velocity of emergence of stock from both the primary headbox andthe secondary headbox should be less than the lineal speed of v thewire.

emergence bearing a ratio to the speed of the wire not less than 0.900nor greater than 1,100;

Obviously, if the velocity of emergence of stock from the primary boxhas a ratio to the wire speed of 0.900, the velocity of emergence ofstock from the secondary box must have the ratio of not less than unityrelative to the velocity of emergence of stock from the primary box.Contype or of the pressure type. Theoretically the versely, if thevelocity of emergence of stock from the primary box relative to the wirespeed has the ratio of 1.100, the velocity of emergence of stock fromthe secondary headbox must have a ratio to the velocity f emergence ofstock from the primary headbox of not more than unity, although it mightwell be less than unity down to 0.900.

So far as the above numerical ratios are con cerned, the velocitiesreferred to are the theoretical velocities of emergence computed asequal to the square root of 2GH in which G is the acceleration ofgravity and H is the static head efiective on the slice measured in feetof water.-

isfactory technique for making such a determination which in any eventwould have to represent an average across a slice opening of 200" inlength. Accordingly, for the purpose of regulation the most satisfactorymeasurement from the standpoint of easy and accurate determination isthe static head measured directly in inches in the case of a gravityhead or in pounds per square inch translated into feet of head in thecase of the so-called pressure type headboxes. I accordinglypropose toregulate the ratios above discussed by regulating the effective heads inthe primary and secondary headboxes.

1 effective heads of the headboxes.

feet on the theoretical velocity,

The heads, of course, vary with the square of the velocity and thenumerical ratios above set forth.

Because of the practical difliculty of obtaining accurate measurement ofthe actual velocity of emergence, I find it sim ler to control thevelocitiesof emergence of stock by controlling the The desired ratiobetween the head in the secondary headbox and that in the primaryheadbox correspond to the velocity ratios above set forth and wouldplace the range of head ratios between 0.810

corresponding to a velocity ratio of 0.900, and

1.210 corresponding to a velocity ratio of 1.100.

The slice openings H's of the secondaryheadbox and H? of the primaryheadbox are indicated because under a few conditions of operation theseopenings might be of suflicient extent to modify the effective head. ,Inrunning extremely heavy basis weights at very low wire speeds theeffective head may be reduced to as little as measuredfrom the bottom ofthe headbox while the slice opening may amount to as much as 2". itiesare determined by measuring the effective head from the center of theslice opening instead-of from the bottom of the box, and in such heightof the slice opening relative to the effec:

tive head is so small that half of the slice opening is ineffective toproduce any substantial ef- Referring now to the drawing in which likenumerals indicate like parts, I have shown a paper and/0r board makingmachine of the Fourdrinier type in order to illustratethe abovedescribed process. The'paper or board machine, well known in the art,comprises a breast, roll l0, a couch roll I2, conventional table rollsl4 and suction boxes Hi. The paper making screen or wire I8 is trainedat one end around the breast roll I0 and at the other end around thecouch .roll l2 which is usually of the suction type. Conventional guideand-tensioning rolls are also provided as is also well known in the art.Positioned over and closely adjacent to the breast roll I0 is theprimary headbox containing a flow evener 22 which serves to assist incontrolling the evenness of flow of the stock emerging from the slice ofthe headbox, the height of which is shown by the arrows H'P. The tablerolls H are rotatably mounted and not only sup- I port the paper makingscreen or wire, but serve also to assist in withdrawing water from thepaper and/or board making stock through the" screen or wire so as toleave the fibres of the stock in a felted mass in web form; The firstset of suction boxes are positioned ahead of'the dandy roll 28 and serveto withdraw sufficient water from the forming web of stock so that thelatter may be properly conditioned to be worked In such case theoreticalvelocdepending upon the length of the wire and the the last group ofsuction boxes. Sumcient suction is used so that by the time the .stockfrom the secondary headbox and the base sheet reach the dandy roll 30,the top surface of the composite sheet is in such condition that it maybe subjected to the action of a dandy roll without damage thereto andwithout breaking the sheet. In other words there is substantially nopond present on the top surface of either the base heet or the topsurface of the secondary stock gmwhen. each is subjected to the actionof the dandy rolls.

As will be appreciated by those skilled in the art the dandy roll shouldoperate ona web of fibrous material while it is as wet as possible.

The web, however, must be sufliciently formed and must be sufficientlydry so as to prevent the'fibres thereof from being picked up by thedandy roll which consists usually merely of a hollow member having awire mesh operating 30 surface. It is universally recognized in thepaper making art that a dandy roll cannot operate successfully if theweb on which it operates is still in a pended condition,that is,the'upper surface of the web cannot be in such watery con- 5 dition thatthe fibres are floating in the water of the paper or board makingfurnish. As I have disclosed and; claimed in my copending applicationSerial No. 252,725, filed January 25, 1939, for Board manufacture, Ihave found that 40 it is possible sufliciently to dehydrate the basesheet so that the pond which would normally exist at the point in thewire where the dandy .-roll 28 is located has disappeared. f v Inoperating the multiple headbox system previously described in accordancewith the process which I have developed, it .will be appreciated that Ican accurately control the amounts of stock deposited by the primary andsecondary headbox,. and can assure a close control ofthe formation ofthe base sheet and the top layer without resorting to make-shiftarrangements. By maintaining a ratio of the respective heads to eachother and to the speed of the wire, vI canprovide at all times anaccurate control of the manufacture of ply board or paper having thesurface characteristics required by the box and container makingindustry.

My invention also contemplates, in connection with the process abovedescribed, the use of varip1e,- use the same variations of stockdisclosed by me inthe aforesaid copending application.

The process lends itself not only to a complete and accurate control ofthe board making process, but also to the formation of a paper and/orboard using all kinds of combinations of fibrous stbcks, the particularcombination used and the order of deposition depending upon the types ofpaper and/or board desired.

It will be appreciated that the invention may be modified considerablywithout departing in any way from the spirit of th invention or thescope of the appended claim which "is to be broadly construed.

' sheet, is immediately subjected to the action of' ous types of stockdepending upon the characteristics ofth board required. I can, for exam-I claim:

A method of making an interfelted cellulosic fibrous web on aFourdrinier machine having a traveling wire, a primary headbox and asecondary headbox each adapted to discharge stock in the direction oftravel of the wire; which comprises laying down stock from said primaryheadbox on the moving fourdrinier wire, dehydrating said stock to form abase sheet to such a point as substantially to eliminate all floatingfibers on the upper surface of said base sheet on the wire, then layingdown a secondary celluiosic fibrous stock from said secondary headbox ontop of said base sheet, drawing the fibers of the secondary stock intointerlocking engagement with the stock forming the base sheet to form acomposite interfelted sheet, regulating the static head effective on theprimary and secondary headboxes to maintain a velocity of emergence ofthe stock from the primary headbox which is less than the lineal speedof the wire but which shall not have a ratio to the wire speed of lessthan 0.900 and to maintain a velocity of emergence of the stock from thesecondary headbox which is less than'the velocity of emergence of thestock from the primary headbox except where the emergence of the stockfrom the primary headbox is at its lower limit of 0.900 and in such caseto maintain a ratio of velocity of emergence of stock from the secondaryheadbox to velocity of emergence of stock from the primary headbox of1.00 and without permitting the ratio of the velocity of emergence ofthe stock from the secondary headbox to the speed of the wire to dropbelow 0.900

ALVIN TUTEN.

